21623731 has 2 divisors, whose sum is σ = 21623732. Its totient is φ = 21623730.

The previous prime is 21623699. The next prime is 21623773. The reversal of 21623731 is 13732612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21623731 - 2⁵ = 21623699 is a prime.

It is a super-2 number, since 2×21623731² = 935171484720722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21623696 and 21623705.

It is not a weakly prime, because it can be changed into another prime (21623131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10811865 + 10811866.

It is an arithmetic number, because the mean of its divisors is an integer number (10811866).

Almost surely, 2^21623731 is an apocalyptic number.

21623731 is a deficient number, since it is larger than the sum of its proper divisors (1).

21623731 is an equidigital number, since it uses as much as digits as its factorization.

21623731 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1512, while the sum is 25.

The square root of 21623731 is about 4650.1323637075. The cubic root of 21623731 is about 278.5972830078.

The spelling of 21623731 in words is "twenty-one million, six hundred twenty-three thousand, seven hundred thirty-one".